Elimination Reactions of Alkyl Halides Zaitsevs Rule

7 Elimination Reactions of Alkyl Halides Zaitsev s Rule 383 

Test your knowledge of Key Ideas by using resources in ThomsonNOW or by answering end-of-chapter problems marked with A. 

Elimination reactions are more complex than substitution reactions for several reasons. There is, for example, the problem of regiochemistry. What 

According to Zaitsev s rule, formulated in 1875 by the Russian chemist Alexander Zaitsev, base-induced elimination reactions generally although not always) give the more stable alkene product—that is, the alkene with more alkyl substituents on the double-bond carbons. In the following two cases, for example, the more highly substituted alkene product predominates. 

We said at the beginning of this chapter that two kinds of reactions can happen when a nucleophile/Lewis base reacts with an alkyl halide. The nucleophile can either substitute for the halide by reaction at carbon or cause elimination of HX by reaction at a neighboring hydrogen  

Alexander M. Zaitsev (1841-1910) was born in Kazan, Russia, and received his Ph.D. from the University of Leipzig in 1866. He was professor at the University of Kazan (1870-1903) and at Kiev University, and many of his students went on to assume faculty positions throughout Russia. 

Look carefully in each reaction at the structure of the substrate, the leaving group, the nucleophile, and the solvent. Then decide from the summaries at the ends of Section 11.5 and this section whether an SN1 or an SN2 reaction is likely to be favored. SN1 reactions are favored by tertiary, allylic, or benzylic substrates, by halide leaving groups, by nonbasic nucleophiles, and by neutral or acidic solvents. S 2 reactions are favored by primary substrates, by halide leaving groups, by good nucleophiles, and by polar aprotic solvents. 

Predict whether each of the following substitution reactions is likely to be SN1 or 

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